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About New 3in Exhaust

This is a discussion on About New 3in Exhaust within the External Engine forums, part of the LSx Technical Help Section category; Hey guys, I have a quick question, I recently had a 3in stainless magnaflow exhaust installed from the manifold back ...

  1. #1
    Member smkn gts's Avatar
    Join Date
    Aug 2008
    wayne, michigan

    1998 Pontiac Trans Am

    About New 3in Exhaust

    Hey guys,

    I have a quick question, I recently had a 3in stainless magnaflow exhaust installed from the manifold back with an electric cut off right after the ory pipe. The exhaust sounds great but there is no back pressure what so ever. My friend with a ws6 seems to think that the lack of back pressure is actually slowing down my car in comparison to the stock exhaust which I dis agree. He says that because other than the lid the car is stock the car needs the back pressure and he thinks i should try a restrictor pipe to see. I dont know if it is a tuning issue but I know the car has a check engine light on as well. I know it sounds like a silly question but could the exhaust really be affecting hp? and would a tune fix any of these issues? I know the computer can greatly affect how the car runs and I was wondering if the computer needs to be tuned for the change from stock to such a large exhaust system!

    I think I will post this in the bolt on section of this site as well!

    Thanks for reading

  2. #2
    Life in the Fast lane sunsetorangess's Avatar
    Join Date
    Aug 2005
    Bragg NC

    Met. Sunset Orange
    01 SS

    If your running stock manifolds than you have your back pressure. Your SES light is on because you eliminated your Cat's and its probly just an emissions code, nothing to worry about, although i would have it scanned and post up the codes to be sure.
    You can have the rear 02's deleted out of the computer by a tune but you do not need a tune. To get the most for your money i would complete all mods and then have a dyno tune or talk to Frost about a mail order tune.
    As far as you needing back pressure you realy dont. Whatever you loose on the bottom end you will gain on the top end so its an even balance.
    2001 SS, Its not the car its the Driver that matters....

  3. #3
    Senior Member karpetcm's Avatar
    Join Date
    Oct 2008
    Tujunga, CA

    01 Camaro 6speed

    Ive heard many people say when you open up your exhaust too much and lose back pressure you lose power and from my own experience and dyno numbers that is simply not true. The car may feel it has less torque and less power in the bottom end but ive always pulled more power HP & TQ. One time a member explained that the power just travles further up the RPM range meaning torque so it feels you have less bottom end or loss of power. People put LT's, ORY, Catback Exhaust and Cutouts with no issue's and the cars pull great numbers RWHP and RWTQ.
    1993 Z28 M6: K&N Intake, 52mm TB, TB Bypass, No Cats, Exhaust Cutout, Flowmaster Muffler, 3.90 Gears, 160 Thermo, Tune, BMR Springs, Bilstein Shocks, 3 Point SFC,s & MGW Shifter.

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